Effects of acute toxicity of the pesticide Chlorpyrifos and the metal Cadmium, both individually and in mixtures, on two species of native neotropical cladocerans.

The excessive use of pesticides in agriculture and the widespread use of metals in industrial activities and or technological applications has significantly increased the concentrations of these pollutants in both aquatic and terrestrial ecosystems worldwide, making aquatic biota increasingly vulnerable and putting many species at risk of extinction. Most aquatic habitats receive pollutants from various anthropogenic actions, leading to interactions between compounds that make them even more toxic. The aim of this study was to assess the effects of the compounds Chlorpyrifos (insecticide) and Cadmium (metal), both individually and in mixtures, on the cladocerans Ceriodaphnia rigaudi and Ceriodaphnia silvestrii. Acute toxicity tests were conducted for the compounds individually and in mixture, and an ecological risk assessment (ERA) was performed for both compounds. Acute toxicity tests with Cadmium resulted in EC50-48 h of 0.020 mg L-1 for C. rigaudi and 0.026 mg L-1 for C. silvestrii, while tests with Chlorpyrifos resulted in EC50-48 h of 0.047 µg L-1 and 0.062 µg L-1, respectively. The mixture test for C. rigaudi showed the occurrence of additive effects, while for C. silvestrii, antagonistic effects occurred depending on the dose level. The species sensitivity distribution curve for crustaceans, rotifers, amphibians, and fishes resulted in an HC5 of 3.13 and an HC50 of 124.7 mg L-1 for Cadmium; an HC5 of 9.96 and an HC50 of 5.71 µg L-1 for Chlorpyrifos. Regarding the ERA values, Cadmium represented a high risk, while Chlorpyrifos represented an insignificant to a high risk.

Ecological Implications on Aquatic Food Webs Due to Effects of Pesticides on Invertebrate Predators in a Neotropical Region.

Predation presents specific behavioral characteristics for each species, and the interaction between prey and predator influences the structuring of the food web. Concerning insects, predation can be affected in different ways, such as exposure to chemical stressors, e.g., pesticides. Therefore, analyses were carried out of the effects of exposure to insecticide fipronil and the herbicide 2,4-D on predation, parameters of food selectivity, and the swimming behavior of two neotropical predatory aquatic insects of the families Belostomatidae (giant water bugs) and larvae of Libellulidae (dragonfly). These predatory insects were exposed for 24 h to a commercial formulation of the chlorophenoxy herbicide, 2,4-D at nominal concentrations of 200, 300, 700, and 1400 µg L-1, and to a commercial formulation of the phenylpyrazole insecticide, fipronil at nominal concentrations of 10, 70, 140, and 250 µg L-1. In a control treatment, the insects were placed in clean, unspiked water. At the end of the exposure, the maximum swimming speed of the predators was evaluated. Afterward, the predators were placed in clean water in a shared environment for 24 h with several prey species, including the cladoceran Ceriodaphnia silvestrii, larvae of the insect Chironomus sancticaroli, the amphipod Hyalella meinerti, the ostracod Strandesia trispinosa, and the oligochaete Allonais inaequalis for 24 h. After this period, the consumed prey was counted. The results reveal that predators from both families changed prey consumption compared with organisms from the control treatment, marked by a decrease after exposure to fipronil and an increase in consumption caused by 2,4-D. In addition, there were changes in the food preferences of both predators, especially when exposed to the insecticide. Exposure to fipronil decreased the swimming speed of Belostomatidae individuals, possibly due to its neurotoxic effect. Exposure to the insecticide and the herbicide altered prey intake by predators, which could negatively influence the complex prey-predator relationship and the functioning of aquatic ecosystems in contaminated areas.

Ecological risk assessment for metals in sediment and waters from the Brazilian Amazon region.

Pollution by metals is a matter of concern around the world. In recent decades, the high population growth in urban centers has significantly magnified the entry of these pollutants into aquatic ecosystems. The Amazon region, intense migratory flow, gold mining, and industrialization have been considered the main driving forces for increasing metal pollution. Thus, the main aim of this study is to conduct, for the first time, an Ecological Risk Assessment (ERA) based on metal concentrations measured in the sediment and water of several aquatic environments from the Amazon basin, based on the risk quotient values (RQ = measured environmental concentration - MEC/predicted no effect concentration - PNEC). In addition, the metal contamination factor (CF) was estimated. Although metal concentrations in water were generally low, these values were far above the limits established by current national legislation in many areas, showing higher concentrations for the metals Co, Pb, Cr, Cu, and Ni. Concentrations of Mn, Cu, Ba, Pb, Co, Ni, Cr, Zn, Cd, and As were especially high in the sediment for several evaluated environments. The ERA for the water compartment revealed that 56% of the studied areas presented high risk (RQ > 1) for aquatic biota. In the sediment, 66% of the sites presented a high risk and 40% medium risk (RQ = 0.1-1). The CF indicated that 49% of the sampling points had high contamination and only 24%, had low contamination. These results reveal that monitoring studies in the Amazon region, provides important information so that public policies for the preservation of water resources can be strengthened in the Amazon.

Toxicity of Binary Metal Mixtures to the Tropical Ostracod Strandesia Trispinosa.

The ecotoxicity of metals is generally assessed individually, in part because current knowledge does not allow for the accurate prediction of the toxicity of metal mixtures to aquatic organisms. The objective of this study was to investigate the toxic effects of binary combinations of metal salts (copper sulphate-CuSO4, cadmium chloride-CdCl2, mercury chloride-HgCl2 and manganese sulphate-MnSO4) on the tropical ostracod Strandesia trispinosa through acute toxicity tests. To this end, ostracods were exposed to each individual metal salt as well as to their combinations by applying a full factorial design. The model that best explained the effects of the mixtures CuSO4 x CdCl2, CuSO4 x HgCl2 and CuSO4 x MnSO4 on the survival of S. trispinosa was Concentration Addition, whereas this was Independent Action for the CdCl2 x HgCl2 mixture. The observed synergistic interactions are likely to result in unacceptable risks to aquatic ecosystems under real field conditions. This is especially the case if CuSO4 predominates the metal mixture, as observed for its combination with mercury and manganese.

Macroinvertebrates responses based on chemical and physical variables in urban streams

The Land uses and occupations around small watersheds generate negative impacts such as deterioration of water quality, environmental simplification, reduced availability of habitats for species, and loss of biodiversity. Benthic macroinvertebrates are an important aquatic community and are widely used in environmental monitoring actions in aquatic ecosystems, including urban streams, which are still little studied in Brazil. In our study, an urban headwater basin (Monjolinho River Basin) was studied on the benthic community structure, together with the physical and chemical variables of the water, as an environmental monitoring tool calculated by RHDEP, TSI, BMWP indexes and abundance-biomass curves. The results showed a gradient of environmental quality, where the best environments are a consequence of preserving the vegetation cover. These environments (Espraiado and Canchim) present groups sensitive to environmental degradation (Ephemeroptera, Plecoptera and Trichoptera), greater diversity and a better structure in the respective benthic macroinvertebrate assemblages. Among the streams sampled, one is very clean, four are moderately polluted, and one is severely polluted. Thus, considering that these streams waters are essential for public supply, actions to clean up and recover degraded environments are urgent and a priority.(AU)

Macroinvertebrates responses based on chemical and physical variables in urban streams

Abstract The Land uses and occupations around small watersheds generate negative impacts such as deterioration of water quality, environmental simplification, reduced availability of habitats for species, and loss of biodiversity. Benthic macroinvertebrates are an important aquatic community and are widely used in environmental monitoring actions in aquatic ecosystems, including urban streams, which are still little studied in Brazil. In our study, an urban headwater basin (Monjolinho River Basin) was studied on the benthic community structure, together with the physical and chemical variables of the water, as an environmental monitoring tool calculated by RHDEP, TSI, BMWP indexes and abundance-biomass curves. The results showed a gradient of environmental quality, where the best environments are a consequence of preserving the vegetation cover. These environments (Espraiado and Canchim) present groups sensitive to environmental degradation (Ephemeroptera, Plecoptera and Trichoptera), greater diversity and a better structure in the respective benthic macroinvertebrate assemblages. Among the streams sampled, one is very clean, four are moderately polluted, and one is severely polluted. Thus, considering that these streams waters are essential for public supply, actions to clean up and recover degraded environments are urgent and a priority.

Macroinvertebrates responses based on chemical and physical variables in urban streams

Abstract The Land uses and occupations around small watersheds generate negative impacts such as deterioration of water quality, environmental simplification, reduced availability of habitats for species, and loss of biodiversity. Benthic macroinvertebrates are an important aquatic community and are widely used in environmental monitoring actions in aquatic ecosystems, including urban streams, which are still little studied in Brazil. In our study, an urban headwater basin (Monjolinho River Basin) was studied on the benthic community structure, together with the physical and chemical variables of the water, as an environmental monitoring tool calculated by RHDEP, TSI, BMWP indexes and abundance-biomass curves. The results showed a gradient of environmental quality, where the best environments are a consequence of preserving the vegetation cover. These environments (Espraiado and Canchim) present groups sensitive to environmental degradation (Ephemeroptera, Plecoptera and Trichoptera), greater diversity and a better structure in the respective benthic macroinvertebrate assemblages. Among the streams sampled, one is very clean, four are moderately polluted, and one is severely polluted. Thus, considering that these streams' waters are essential for public supply, actions to clean up and recover degraded environments are urgent and a priority.

The influence of black spot disease on the relative condition factor of Astyanax paranae Eigenmann, 1914 (Characiformes: Characidae) in Brazilian subtropical streams

Environmental disturbances and their consequences require constant studies to understand how communities and their ecological relationships respond to these processes. Through analysis of the host-parasite relationships, it is observed that the effect of these disturbances is variable and can change the physiology or behavior of organisms. Black spot disease, caused by endoparasitic helminths, is a pathology observed in natural environments, however, there is not much information about the consequences of this infestation. We separated the specimens from each stream into parasitized and non-parasitized groups, which were subjected to biometric analysis. The biometrics involved cysts count and weight-length measures, which were used to analyze the average relative condition factor. Additionally, we correlate these measures with the parasitic burden of infected individuals. Finally, the parasitized individuals were submitted to histological sections to recognize the parasite. The results demonstrate a low physiological condition in the parasitized group, when compared with non-parasitized groups from the same stream and from different streams. This suggests that pollution, in addition to effects of infestation worsen the fish condition. Besides, the parasite burden was negatively correlated with the condition factor, weight and length measures. We conclude that the parasite burden negatively affects Astyanax paranae individuals´ physiological condition and that trematodes also occur in polluted environments.(AU)

The influence of black spot disease on the relative condition factor of Astyanax paranae Eigenmann, 1914 (Characiformes: Characidae) in Brazilian subtropical streams

Environmental disturbances and their consequences require constant studies to understand how communities and their ecological relationships respond to these processes. Through analysis of the host-parasite relationships, it is observed that the effect of these disturbances is variable and can change the physiology or behavior of organisms. Black spot disease, caused by endoparasitic helminths, is a pathology observed in natural environments, however, there is not much information about the consequences of this infestation. We separated the specimens from each stream into parasitized and non-parasitized groups, which were subjected to biometric analysis. The biometrics involved cysts count and weight-length measures, which were used to analyze the average relative condition factor. Additionally, we correlate these measures with the parasitic burden of infected individuals. Finally, the parasitized individuals were submitted to histological sections to recognize the parasite. The results demonstrate a low physiological condition in the parasitized group, when compared with non-parasitized groups from the same stream and from different streams. This suggests that pollution, in addition to effects of infestation worsen the fish condition. Besides, the parasite burden was negatively correlated with the condition factor, weight and length measures. We conclude that the parasite burden negatively affects Astyanax paranae individuals´ physiological condition and that trematodes also occur in polluted environments.

Life-History Traits Response to Effects of Fish Predation (Kairomones), Fipronil and 2,4-D on Neotropical Cladoceran Ceriodaphnia silvestrii.

Aquatic environments are constantly exposed to a cocktail of contaminants mainly due to human activities. As polluted ecosystems may simultaneously present other multiple natural stressors, the objective of the present study was to evaluate joint effect of stressors (natural and anthropogenic) on life history traits of the Neotropical cladoceran, Ceriodaphnia silvestrii. For this purpose, the effects of water conditioned with predator kairomones (fish) and environmental concentrations (sublethal) of two pesticides widely used in sugarcane monoculture in Brazil, the insecticide Regent® 800 WG (active ingredient-a.i. fipronil) and the herbicide DMA® 806 BR (a.i. 2,4-D) were evaluated using chronic toxicity testing, isolated and in mixture, for this cladoceran species. The environmental risks of pesticides for tropical freshwater biota were also estimated from the risk quotient MEC/PNEC. Among the characteristics of the life history of C. silvestrii evaluated after 8 days of exposure, compared with the mean value of control, the age of primiparous females was not affected by any evaluated treatment. However, species average survival decreased in the treatment of kairomones mixed with fipronil (FK) and in the treatment with a mixture of fipronil, 2,4-D, and kairomones (MFKD). The body length of maternal females was shorter than in the control after exposure in treatments with only kairomones (K) and FK. Fecundity of this cladoceran was reduced when exposed to FK and MFKD treatments, and the intrinsic rate of population increase significantly decreased for organisms exposed to treatment with fipronil (F) and to mixtures of fipronil and 2,4-D (MFD), MFDK, and FK. The results indicated that the combination of anthropogenic and natural stressors causes changes in C. silvestrii life history traits, which can contribute to the decline in populations, and our preliminary risk assessment results are a matter of concern regarding biota conservation.

Effects of abamectin-based and difenoconazole-based formulations and their mixtures in Daphnia magna: a multiple endpoint approach.

This study evaluated the toxicity of pesticide formulations Kraft® 36 EC (active ingredient-a.i. abamectin) and Score® 250 EC (a.i. difenoconazole), and their mixtures in Daphnia magna at different biological levels of organization. Survival, reproduction and biochemical markers (cholinesterase (ChE), catalase (CAT) and lipid peroxidation (LPO)) were some of the endpoints evaluated. Total proteins and lipids were also studied together with energy consumption (Ec). D. magna neonates were exposed for 96 h to Kraft (2, 4, and 6 ng a.i./L) and Score (12.5, 25, and 50 µg a.i./L) for the biochemical experiments, and for 15 days to abamectin (1-5 ng a.i./L) and to difenoconazole (3.12-50 µg a.i./L) to assess possible changes in reproduction. Exposures of organisms to both single compounds did not cause effects to antioxidant and detoxifying enzymes, except for LPO occurring at the highest concentration of difenoconazole tested. For ChE and CAT there was enzymatic induction in mixture treatments organisms, occurring at minor pesticides concentrations for CAT and at the two highest concentrations for ChE. There were no significant differences for total protein in D. magna but lipids showed an increase at the highest concentrations of pesticide mixture combinations. There was a significant increase of Ec in individuals of all treatments tested. In the chronic test, increased fecundity occurred for D. magna under difenoconazole exposures and mixtures. This study demonstrated that mixtures of these pesticides caused greater toxicity to D. magna than when tested individually, except for Ec. Therefore, effects of mixtures are very hard to predict only based on information from single compounds, which most possibly is the result of biological complexity and redundancy in response pathways, which need further experimentation to become better known.

Isolation of Naegleria spp. from a Brazilian Water Source.

The genus Naegleria, of the free-living amoeba (FLA) group, has been investigated mainly due to its human health impact, resulting in deadly infections and their worldwide distribution on freshwater systems. Naegleria fowleri, colloquially known as the "brain-eating amoeba," is the most studied Naegleria species because it causes primary amoebic meningoencephalitis (PAM) of high lethality. The assessment of FLA biodiversity is fundamental to evaluate the presence of pathogenic species and the possibility of human contamination. However, the knowledge of FLA distribution in Brazil is unknown, and to rectify this situation, we present research on identifying Naegleria spp. in the Monjolinho River as a model study. The river is a public Brazilian freshwater source that crosses the city of São Carlos, in São Paulo state, Brazil. Five distinct sampling sites were examined through limnological features, trophozoites culturing, and PCR against internal transcribed spacer (ITS) regions and 5.8S rRNA sequences. The results identified N. philippinensis, N. canariensisi, N. australiensis, N. gruberi, N. dobsoni sequences, as well as a Hartmannella sequence. The methodology delineated here represents the first Brazilian Naegleria spp. study on a freshwater system. Our results stress the urgency of a large scale evaluation of the presence of free-living amoebas in Brazil.

Sensitivity of tropical cladocerans to chlorpyrifos and other insecticides as compared to their temperate counterparts.

The use of temperate toxicity data in tropical risk assessments has often been disputed. Previous sensitivity comparisons between temperate and tropical species, however, have not shown a consistent sensitivity difference between climatically-distinct species. Such comparisons were often limited by a small tropical toxicity dataset. In addition, differences in the taxonomic compositions of the temperate and tropical species assemblages used to construct species sensitivity distributions curves also hampered direct comparisons (e.g. type and ration of crustaceans and insects). The aim of the present study was to compare the sensitivity of temperate and tropical cladocerans to insecticides. Acute laboratory toxicity tests were conducted with five Neotropical cladocerans exposed to a concentration series of the insecticide chlorpyrifos. Subsequently, their EC50 values were compared with those reported in the literature for non-tropical cladocerans. An additional literature toxicity data search for insecticides other than chlorpyrifos was also conducted for both temperate and tropical cladocerans to enable a comparison for a wider range of insecticides and taxa. The order of sensitivity of the native cladocerans to chlorpyrifos was Ceriodaphnia silvestrii (0.039 µg L-1) > Diaphanosoma birgei (0.211 µg L-1) = Daphnia laevis (0.216 µg L-1) > Moina micrura (0.463 µg L-1) = Macrothrix flabelligera (0.619 µg L-1). A regulatory acceptable concentration based on temperate cladoceran toxicity data of both chlorpyrifos and other insecticides also appeared to be sufficiently protective for tropical cladoceran species. Implications for the use of temperate toxicity data in tropical risk assessments and indications for tropical cladoceran test species selection are discussed.

Freshwater neotropical oligochaetes as native test species for the toxicity evaluation of cadmium, mercury and their mixtures.

The toxicity of metals, whether isolated or in mixtures, involves changes in biochemical processes as well as in cell membranes, which may lead to deleterious short- and long-term effects on the affected organisms. Among metals, cadmium and mercury stand out due to their abundance in nature, frequent use for industrial activities and biological accumulation, with high levels of residence in trophic chains. Benthic communities are particularly prone to metal pollution since metals usually accumulate in sediments. The aim of this study was to evaluate the acute toxicity of mercury and cadmium, single and in mixture, to two native species of epibenthic oligochaetes: Allonais inaequalis and Dero furcatus. In order to assess the potential of these species as bioindicators, we compared their sensitivity with those of other internationally used species by applying the species sensitivity distribution approach. The 96h-LC50 of cadmium chloride was 627 and 364 µg L-1 for A. inaequalis and D. furcatus, respectively, evidencing that the latter species is almost twice as sensitive to this metal than A. inaequalis. For mercury chloride, the 96h-LC50 was 129 µg L-1 for A. inaequalis and 92 µg L-1 for D. furcatus. The sensitivities of these oligochaetes were superior or similar to that of other frequently used oligochaete test species such as Tubifex tubifex and Lumbriculus variegatus. The metal mixtures had synergism in general (D. furcatus) or at high doses only (A. inaequalis), implying a potentiation of their toxic effects when both metals co-occur in the environment. By comparing the derived toxicity values with concentrations of cadmium and mercury measured in the field, it can be concluded that aquatic organisms are likely to be at risk when exposed to the environmental relevant concentrations of cadmium and mercury here tested, especially when they are both present.

Sensitivities of three tropical indigenous freshwater invertebrates to single and mixture exposures of diuron and carbofuran and their commercial formulations.

As compared to their temperate counterparts, few toxicity tests have been conducted so far into the evaluation of the sensitivity of indigenous tropical species to pesticides. Especially mixture toxicity assessments appear to be scarce. To contribute to increase our knowledge in this arena, we evaluated the acute toxicity of diuron and carbofuran and their mixtures to the neotropical oligochaetes Allonais inaequalis and Dero furcatus, and the ostracod Strandesia trispinosa. Tests were performed with both the pure active ingredients, as well as their formulated products. The toxicity of the latter to the three test organisms was generally greater than that of the pure active ingredients, although absolute differences were rather small. The sensitivity of the indigenous species was slightly greater than temperate test species from the same taxonomic groups. The concentration addition conceptual model best described the results of the mixture toxicity data. Derived deviations of this model appeared to be dependent on the test organism and as to whether the pesticides were applied as active ingredients or their commercial products. Reported field concentrations of the two pesticides indicate risks to freshwater biota, especially if they are both present. The test species used in the present study are concluded to be suitable candidates as surrogate test organisms in local pesticide risk evaluations.

Predation and reproductive performance in two pelagic typhloplanid turbellarians.

We investigated feeding and reproductive performance of coexisting pelagic turbellarians from experiments on predation rates of Mesostoma ehrenbergii and M. craci as a function of food (Daphnia similis, three levels) and temperature (4 levels) during 10 days. Flatworms were collected from the pelagic of a subtropical lake in Brazil. Growth was more rapid at higher temperatures: more prey were consumed, and more eggs produced. M. craci and particularly M. ehrenbergii fitted a linear mixed-effects model and showed a type II functional response. M. craci was the more stenothermic of the two. Intrageneric predation also occurred: M. ehrenbergii fed on M. craci, but not vice versa. After a first clutch of subitaneous eggs, M. ehrenbergii produced resting eggs only. In M. craci an intermediate type of eggs hatched some time after release, survived passage through the gut of M. ehrenbergii, but did not resist drying. By primarily selecting cladoceran prey, M. ehrenbergii can make coexistence of both flatworms possible. As population density of M. ehrenbergii increases, it turns to producing resting and non-viable subitaneous eggs, thus limiting its population size. In nature, these processes structure the zooplankton community, while avoiding extinction of prey and predator.

Acute and chronic toxicity of diuron and carbofuran to the neotropical cladoceran Ceriodaphnia silvestrii.

In order to contribute to the increase of the body of knowledge on the sensitivity of tropical indigenous species to pesticides, acute and chronic toxicity tests were conducted with the neotropical cladoceran Ceriodaphnia silvestrii. Tests were carried out with the active ingredients diuron and carbofuran and one of their commercial formulations, the Diuron Nortox® 500 SC and the Furadan® 350 SC, respectively. For carbofuran, the active ingredient was more toxic than the commercial product, whereas for diuron, the commercial product appeared more toxic. In addition, hormetic effects on fertility were recorded for intermediate diuron concentrations. Acute and chronic toxicity data indicated that C. silvestrii was among the most sensitive invertebrate species for both test compounds. Based on concentrations measured in Brazilian water bodies, these compounds represent ecological risks for causing direct and indirect toxic effects on C. silvestrii and other aquatic organisms. Our results support previous claims on the advantages of using native species to better tune ecological risk assessment of chemicals in tropical ecosystems.

Life cycle traits of Philodina roseola Ehrenberg, 1830 (Rotifera, Bdelloidea), a model organism for bioassays.

This paper describes experimental results on the life cycle of the rotifer Philodina roseola cultured in the laboratory. Detailed information on life-cycle parameters of a certain species provides a deep understanding and contributes to a better knowledge of the role of the species in the community, besides providing data that are basic to other ecological investigations such as secondary production estimates and knowledge for applications such as its utilization as test-organism in ecotoxicological studies. The average duration of embryonic development of P. roseola was 23.88 h, the age at maturity of primipara was 3.5 days and the maximum lifespan was 23 days. The average size of the rotifer neonate was 198.77 µm, the mean size of primipara was 395.56 µm and for adults 429.96 µm. The average fecundity was 1.22 eggs per female per day and the mean number of eggs produced per female during the entire life was 22.33. The deceleration of somatic growth from the start of the reproductive stage represents a trade-off between growth and reproduction that is often seen in micrometazoans. The life history of P. roseola follows the strategy of other bdelloid species characterized by a rapid pre-reproductive development and canalization of most assimilated energy to reproduction after reaching maturity. The differences observed in total fecundity and longevity between our P. roseola cultures and those from previous studies were probably due to differences of intrinsic adaptation of this species ecotypes to the conditions of their natural environments.

TAXAS DE FILTRAÇÃO E INGESTÃO DE UMA MICROALGA POR Philodina roseola (Rotifera: Bdelloidea) / Rates of Filtration and Ingestion of a Microalga by Philodina roseola (Rotifera: Bdelloidea) / Tasas de filtración e ingestión de una microalga por Philodina roseola (Rotifera: Bdelloidea)

Rotíferos possuem um importante papel nos ciclos biogeoquímicos e na produtividade orgânica dos ecossistemas de água doce em decorrência de suas elevadas taxas metabólicas. Informações sobre a filtração, seu principal processo de aquisição de energia, são relevantes e ainda escassos para a região tropical. Os rotíferos da Subclasse Bdelloidea alimentam-se por filtração ou raspagem consumindo pequenos itens alimentares, como bactérias, algas, leveduras ou matéria orgânica particulada. Sabemos pouco sobre o papel que desempenham na dinâmica trófica dos habitats que ocupam e por isso o objetivo deste estudo foi quantificar em laboratório as taxas de filtração e ingestão do rotífero Philodina roseola, alimentado com Raphidocelis subcapitata. O delineamento experimental consistiu na exposição de 10 rotíferos adultos por tratamento, em cinco concentrações que variaram entre 10(4) e 10(7) cels mL-1, mantidos sob temperatura de 25 ± 1 °C. Os experimentos tiveram a duração de 1 hora e as concentrações iniciais e finais da suspensão algal foram quantificadas por contagem numérica das células em câmara de Neubauer. Não foram encontradas diferenças significativas entre as concentrações iniciais e finais de células nos controles indicando não ter ocorrido crescimento algal. As taxas de filtração de P. roseola variaram entre 0,09 e 0,25 mL ind-1 h-1. Tendo em vista que a filtração é o principal processo de aquisição de energia de Philodina roseola, assim como dos demais rotíferos, e que está relacionada a questões importantes da dinâmica trófica dos ecossistemas aquáticos, informações adicionais são desejáveis mas necessitam, no entanto, ser ampliadas para outros tipos de alimento e para diferentes combinações de condições experimentais.

Rotifers play an important role in biogeochemical cycles and organic productivity of freshwater ecosystems due to their high metabolic rates. Information on filter feeding, their main process of energy acquisition, are relevant and still scarce for tropical regions. The rotifers of the class Bdelloidea feed by filtration or scraping consuming small food items, such as bacteria, algae, yeasts or particulate organic matter. We know little of their role in the trophic dynamics in the habitats they occupy and so the aim of this study was to quantify laboratory filtration and ingestion rates of the rotifer Philodina roseola, fed with Raphidocelis subcapitata. The experiment consisted of 10 adult exposure treatment at five concentrations approximately in the range between 10(4) and 10(7) cells mL-1, at the temperature of 25 ± 1 °C. The experiments lasted one hour and initial and final concentrations of the algal suspensions were determined by counting the number of cells in a Neubauer chamber. There were no significant differences between the initial and final concentrations of cells in the control group indicating that algal growth did not occur. Philodina roseola filtration rates varied between 0.09 and 0.25 mL ind-1 h-1. Given that filtration is the main process of energy acquisition by Philodina roseola, as well as for most other rotifers, and that it comprises important issues related to trophic dynamics of aquatic ecosystems, additional experimental information is especially important and need to be extended to other types of food and combinations of experimental conditions.

Los rotíferos desempeñan un importante papel en los ciclos biogeoquímicos y en la productividad orgánica de los ecosistemas de agua dulce como consecuencia de sus elevadas tasas metabólicas. Es relevante la información sobre la filtración, su principal proceso de adquisición de energía, la cual es todavía escasa para la región tropical. Los rotíferos de la subclase Bdelloidea se alimentan por filtración o raspaje, consumiendo pequeños elementos alimentícios, como bacterias, algas, levaduras o materia orgánica particulada. Sabemos poco del papel que desempeñan en la dinámica trófica de los hábitats que ocupan, y por eso el objetivo de este estudio fue cuantificar en laboratorio las tasas de filtración e ingestión del rotífero Philodina roseola, alimentado con Raphidocelis subcapitata. El experimento consistió en la exposición de diez adultos por tratamiento en concentraciones entre 1x10(4) y 1x10(7) células mL-1 y bajo temperatura de 25±1 °C. Los experimentos tuvieron la duración de una hora y las concentraciones iniciales y finales de la suspensión algal fueron cuantificadas por conteo numérico de las células en cámara de Neubauer. No fueron encontradas diferencias significativas entre las concentraciones iniciales y finales de células en los controles, lo cual indica que no se presentó crecimiento algal. Las tasas de filtración de P. roseola variaron entre 0,09 y 0,25 mL ind-1 h-1. Teniendo en cuenta que la filtración es el principal proceso de adquisición de energía de la Philodina roseola, así como de los demás rotíferos, y que comprende cuestiones importantes relacionadas con la dinámica trófica de los ecosistemas acuáticos, es importante ampliar la información con experimentos usando otros tipos de alimento y diferentes combinaciones de las condiciones experimentales.

Effects of diuron and carbofuran pesticides in their pure and commercial forms on Paramecium caudatum: The use of protozoan in ecotoxicology.

Toxic effects of diuron and carbofuran on Paramecium caudatum were evaluated. Acute and chronic tests were conducted with diuron and carbofuran active ingredients and their commercial formulations, Diuron Nortox(®) 500 SC and Furadan(®) 350 SC, respectively. The sensitivity range of P. caudatum to reference substance sodium chloride was established. A preliminary risk assessment of diuron and carbofuran for Brazilian water bodies was performed. The tests indicated that toxicity of pure diuron and its commercial formulation was similar, while the commercial product carbofuran was more toxic than its pure form. In acute tests, readings were carried out at 2, 3, 4 and 6 h and showed an increase of mortality with increasing exposure time. The sensitivity of P. caudatum to NaCl ranged from 3.31 to 4.44 g L(-1), averaging 3.88 g L(-1). For diuron, the 6 h LC50 was 64.6 ± 3.3 mg L(-1) for its pure form and 62.4 ± 2.5 mg L(-1) for its commercial formulation. Carbofuran active ingredient was less toxic than that of diuron, presenting a 6 h LC50 of 142.0 ± 2.4 mg L(-1) for its pure form and 70.4 ± 2.2 mg L(-1) for its commercial product. Chronic tests showed that these pesticides cause significant decrease on population growth, generation number and biomass of P. caudatum. The 24 h IC50 was 7.10 ± 0.58 mg L(-1) for pure diuron, 6.78 ± 0.92 mg L(-1) for commercial diuron, 22.95 ± 3.57 mg L(-1) for pure carbofuran and 4.98 ± 0.62 mg L(-1) for commercial carbofuran. Preliminary risk assessment indicated that diuron and carbofuran present potential ecological risks for Brazilian water bodies. P. caudatum was a suitable and sensitive test organism to evaluate diuron and carbofuran toxicity to freshwater protozooplankton and, taking into account the relevant role of protozoans in aquatic environments, we strongly recommend its inclusion in ecotoxicological studies.